Continuing on from this post:

https://drupal.star.bnl.gov/STAR/blog/dmawxc/update-05292019-run-9-embedding-all-vs-matched-reconstructed-tracks-bug-found

We wanted to look closer at the tracks which don't have an MC particle matched to them. It might be that these are pile-up tracks. But since we see tracks at 8 GeV/c or so that don't have a match, what's the probability of that?

These plots compare the DCA, pTtrk, and pTfrac (= pTreco / pTmc) distributions for matched and unmatched tracks. If the unmatched tracks are pile-up, they should have a softer pTtrk distribution and a broader DCA distribution.

We do indeed see such differences in pTtrk and DCA, but the differences are small. As might be expected, the differences in pTfrac are substantial. However, I'm not sure what the unmatched pTfrac distribution tells me about the physics (if it says anything at all)...